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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        /**
         * 可用new Number()定义，valueOf()取值，但不推荐
         * Number.isInteger()
         * toFixed()
        */
        const n = new Number(123)
        console.log(n.valueOf());

        const num = 12, num2 = 12.13445
        console.log(Number.isInteger(num)); // true
        console.log(Number.isInteger(num2)); // false

        console.log(num2.toFixed(2)); // 12.13
    </script>
</body>
</html>